[Algorithms] portal engines in outdoor environments

[Charles B. <cb...@cb...>]

.. is a hopeless proposition, I think.  I'd just like you
guys to check my reasoning before I give up.  Consider,
for example, a building placed on a landscape.  The goal
is to construct portals so that when you stand on one
side of the building, you can't see the other.  If the
player is constrained to stay on the ground, this is
easy enough, it's really a 2d occlusion problem, and you
need 8 portals (two * 4 faces of a square in 2d; two portals
cuz you need one on each side of a face of the square,
parrallel to that face) which splits the universe into 9
zones (8 outside and one inside the occluding cube).

However, if we have a plain cube in 3d and the player can
go anywhere around it, we need 48 portals !! (8 for each of
the 6 faces on the cube).  Now if you have two cubes near
eachother, you need massive numbers of portals, and they
must all not intersect with eachother or other geometry.
This quickly becomes unworkable.

I think something like a "real-time" occcluder (shadow volumes,
etc.) is the only hope for outdoors.

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Charles Bloom           www.cbloom.com